The present invention relates to semiconductor device fabrication. More particularly, the present invention relates to a method of forming a carbon-on-insulator substrate utilizing an in-place bonding method.
The exceptionally high intrinsic carrier mobility of graphene makes it a potentially promising material for high frequency electronic devices such as low-noise amplifiers for communication applications. However, existing methods to prepare the required single-layer or few-layer graphene are far from ideal. Graphene from exfoliation of graphite provides a good quality material, but the yield is low and the inspection requirements are daunting. Graphene layers prepared by thermal treatment of a single crystal SiC layer can provide large area graphene, but processing is difficult (given the requirements for temperatures exceeding 1100° C.-1200° C.) and the SiC template crystals are expensive and limited in size.
Chemical vapor deposition methods for forming graphene on various metal template layers such as Ni have recently been demonstrated and appear promising. See, for example, A. Reina et al. “Large Area, Few-Layer Graphene Films on Arbitrary Substrates by Chemical Vapor Deposition,” in Nano Letters 9, 30 (2009). However, since device layer graphene must be situated on an insulating substrate, the graphene cannot remain on the metal layer on which the graphene has been grown.
This problem has been previously addressed by coating a polymer layer such as, for example, PMMA (polymethyl methacrylate) on the graphene surface and then performing various processing steps to produce a free-standing PMMA-graphene couple which is then bonded graphene face down to a substrate such as thermally oxidized silicon. See, for example, the publication to A. Reina et al. mentioned above as well as the publication to A. Reina et al. entitled “Transferring and Identification of Single and Few-Layer Graphene on Arbitrary Substrates,” J. Phys. Chem. C 112 17741 (2008). While such a transfer/bonding method can be used in forming a graphene-on-insulator substrate, it is not expected to scale well into large areas.
It would therefore be desirable to have a robust and scalable method for transferring and bonding graphene formed on a metal layer to an insulating substrate or insulating substrate layer.